OCT-based ophthalmological measurement system

Abstract

OCT-based ophthalmological measurement system, consisting of a light source with a center-of-mass wavelength λ, an interferometric measurement arrangement, a scanner system which, in addition to the lateral deflection of the sample beam, also causes axial modulations with a frequency f in the sample arm, and a control and evaluation unit, characterized in that the measurement system is a swept-source OCT system and the tuning time dλ / dt of the tunable light source is adapted to the desired maximum measurement depth z and the frequency f of the axial modulation of the scanner system, and the amplitude z M the axial modulation of the scanner system during the tuning time dλ / dt is more than λ / 10 to λ / 2 and in particular also more than 1µm.

Description

[0001] The present invention relates to an ophthalmological measuring system for determining distances or for tomographic imaging of eye structures, which is based on an OCT method.

[0002] According to the state of the art, methods and measuring devices based on confocal scanning systems or optical coherence tomography (OCT) have proven effective for determining distances or for tomographic imaging of eye structures.

[0003] The major technological advantage of OCT is the decoupling of depth resolution from transverse resolution. Unlike microscopy, this allows the three-dimensional structure of the object under investigation to be captured. The purely reflective and therefore non-contact measurement enables the generation of microscopic images of living tissue (in vivo).

[0004] Optical coherence tomography (OCT) uses coherent light with an interferometer to measure distance and create images of reflective and scattering samples. In the human eye, OCT scans produce measurable signals due to changes in refractive index at optical interfaces and volume scattering. Optical coherence tomography is a highly sensitive and fast interferometric imaging technique that has become widely used, particularly in medicine and basic research. OCT images (OCT scans) of eye structures are frequently used in ophthalmology for diagnosis, treatment monitoring, surgical planning, and implant selection.An example of OCT-assisted diagnosis is the use of OCT scans of the retina to determine retinal nerve fiber layer (RNFL) thickness for the diagnosis of glaucoma and for monitoring disease progression.

[0005] The basic principle of the OCT method, described for example in US 5,321,501 A, is based on white-light interferometry and compares the transit time of a backscattered sample signal (or measurement signal) with a reference signal using an interferometer (usually a Michelson interferometer). The arm with a known optical path length (= reference arm) serves as the reference for the measurement arm, in which the sample is located. The interference of the signals from both arms produces a pattern from which the scattering amplitudes can be determined as a function of the optical delay between the arms, thus yielding a depth-dependent scattering profile, which, in analogy to ultrasound technology, is called an A-scan. Rapid variations in the optical delay between the measurement and reference arms can be achieved, for example, using fiber optic links (EP 1,337,803 A1) or so-called rapid-scanning optical delays (RSOD) (US 6,654,127 B2).In multidimensional raster scanning methods, the beam is guided transversely in one or two directions, allowing for the acquisition of a planar B-scan or a three-dimensional volume tomogram. If the reference arm length is kept constant, a planar C-scan can be obtained by scanning the measuring beam laterally in two directions.

[0006] In this process, the arm with a known optical path length (reference arm) serves as the reference for the measuring arm (also called the sample arm). The interference of the signals from the reference and sample arms results in an interference pattern from which the relative optical path length of scattered signals within an A-scan (depth signal) can be determined. In one-dimensional scanning methods, the beam is then guided transversely in one or two directions, analogous to ultrasound technology, allowing for the acquisition of a two-dimensional B-scan, a C-scan, or a three-dimensional tomogram. A C-scan is usually understood to be a two-dimensional tomogram obtained by two-dimensional scanning with a constant reference arm length in a time-domain OCT. However, in the following, this term will be used synonymously for all scans based on two-dimensional scanning, including volumetric scans.The amplitude values ​​of the individual A-scans are displayed as linear or logarithmic grayscale or false-color values. It is also known that volume scans can be corrected for disturbances caused by sample movement by comparison with B-scans (US 7,365,856 B2). According to [1], A.H. Bachmann et al. further reported that phase-resolved measurements, particularly Doppler signal analysis, can provide and display additional information about dynamic processes.

[0007] A-scans are typically acquired at 400 Hz to 400 kHz, and in exceptional cases even in the MHz range. Ophthalmic OCT systems typically exhibit sensitivities of 80 dB to 110 dB. The wavelength used depends on the desired scan area and the absorption and scattering characteristics of the tissue. Retinal OCTs usually operate in the range of 700 nm to 1100 nm, while anterior chamber OCTs preferentially use longer wavelengths, for example, 1300 nm, which are absorbed in the vitreous humor. Anterior chamber OCTs can also be achieved by switching retinal OCTs (US 2007 / 0291277 A1).

[0008] The axial measurement resolution of the OCT method is determined by the so-called coherence length of the light source used, which is inversely proportional to the bandwidth of the radiation and is typically between 3 µm and 30 µm (short-coherence interferometry). The lateral measurement resolution is determined by the cross-sectional area of ​​the measurement beam in the scan area and is between 5 µm and 100 µm, preferably below 25 µm. Due to its particular suitability for examining optically transparent media, the method is widely used in ophthalmology.

[0009] US Patent 2010 / 0110376A1 describes a solution for adjusting the imaging resolution in optical tomography. The goal of this solution is to enable the rapid generation of a live facial view solely from the OCT scanner. However, this can only be achieved by trading axial resolution for increased acquisition speed, allowing the OCT system to deliver enface views quickly and thus eliminating the need for a separate fundus viewing system.

[0010] Two basic types of optical coherence tomography (OCT) have become established in ophthalmology. In the first type, the length of the reference arm is varied, and the intensity of the interference is continuously measured without considering the spectrum. This method is called "time domain" OCT (US 5,321,501 A). In the other type, called "frequency domain" OCT, the spectrum is taken into account, and the interference of the individual spectral components is recorded. Therefore, one speaks of the signal in the time domain (FD-OCT) and the signal in the frequency domain (FD-OCT).

[0011] The advantage of the "Frequency Domain" method lies in its simple and fast simultaneous measurement, which allows for the determination of complete depth information without the need for moving parts. This increases stability and speed (US 7 330 270 B2).

[0012] In frequency domain OCT, a further distinction is made between whether the spectral information is obtained using a spectrometer (“spectral domain OCT”, SD-OCT) or by means of the spectral tuning of the light source (“swept source OCT”, SS-OCT).

[0013] A device for swept-source optical coherence domain reflectometry, capable of measuring an entire eye in a single A-scan, is described in the unpublished German patent application DE 10 2008 063 225 A1. The device comprises a tunable laser light source with a defined spectral linewidth and tuning rate, as well as at least one receiver for the light backscattered from the sample. This enables efficient and cost-effective distance measurements along the entire length of the eye, as, despite typical eye movements of up to 1000 µm / s and with only moderate requirements for the laser light source's tuning rate, disruptive signal losses due to sample displacement during distance measurements between surfaces of the cornea, cornea, and retina are avoided.

[0014] The solution described in US 2008 / 0165366A1 is also based on a swept-source OCT (SS-OCT) that uses a semiconductor optical amplifier (SOA) to provide low polarization-dependent gain (PDG). This gain virtually eliminates all variations in the polarization state of the light at the laser output, but it does not eliminate intra-sweep variations in the polarization state at the laser output, which can negatively impact the performance of the SS-OCT system. The described solution enables stable, low-noise, and efficient operation of swept-source OCT (SS-OCT) systems at high speed with continuous real-time image display.

[0015] The major advantage of OCT methods, as already mentioned, lies in the non-contact measurement and the generation of microscopic images and even three-dimensional structures of the object under investigation, and especially of living tissue (in vivo). A potential source of error that hinders the generation of accurate measurements and topograms is sample movement during the measurement process. According to the prior art, it is known that the effects of sample movement can be reduced by using swept-source OCT (SS-OCT) or pulsed spectral-domain OCT (SD-OCT).

[0016] SH Yun et al. [2] state that the pronounced motion artifacts generated by movement of the sample and / or probe during the exposure time can be significantly reduced by short illumination of individual CCD pixels. Pulsed or tunable broadband light sources are used for this purpose. Axial profiles of a sample with greatly reduced motion artifacts can be generated using so-called "snapshot" illumination. It has been found that the use of pulsed or tunable broadband light sources can represent a viable alternative to the use of expensive high-speed cameras in conjunction with time-domain techniques.

[0017] The solution described in US 7,336,366 B2 concerns the reduction of ambiguities and artifacts in optical coherence tomography (OCT) interferograms. Specifically, the reference light signal is frequency-shifted relative to the sample light signal to separate and superimpose a positive and a negative shift of a complex conjugate component of the OCT interferogram. Appropriate modulators are provided in the beam paths for the reference light and the sample light to achieve this frequency shift.

[0018] Besides the movement of the sample and / or the probe, measurement results can also be negatively affected by unintentional movements of the scanner system. In particular, those movement components that vary the optical path length from the measurement system to the sample and back disrupt interference within the measurement system and thus the measurement results. These disruptive variations in the optical path are referred to below as "axial modulation" by the scanner.

[0019] While the movements of the sample and / or probe are slow, with speeds of a few mm / s, i.e., a few Hz, and can be compensated relatively easily, this is no longer the case for the rather high-frequency, axial modulations of the scanner system.

[0020] According to current technology, the axial modulations occurring in scanner systems are not compensated for, but rather avoided or at least minimized through the use of high-quality scanners. This typically involves the use of single-axis scanners with low mechanical deflections perpendicular to the axis of rotation (torsional modes). To prevent fringe washout, known OCT systems reduce the acquisition time τ for an A-scan to much less than 1 / f and / or use scanner systems with axial modulation amplitudes well below λ / 2. However, both approaches are very expensive.

[0021] An example of the use of such stable scanners is given in [4]. Here, these scanners are used for the decentered deflection of a measurement beam in order to realize very small, defined phase modulations of the optical path in the measurement arm or Doppler shifts, which allow for the reconstruction of full or complex FD-OCT signals. The usable modulations are limited by the onset of fringe washout in the SD-OCT system used.

[0022] For particularly stable scanning, either uniformly rotating polygon mirrors or oscillating galvanometer mirrors are used. While polygon mirrors can scan very quickly and stably, they are fixed to a specific deflection pattern in a particular direction. They are also very noisy and expensive. In contrast, galvanometer mirrors can produce various scan patterns, but require a very complex electronic control system. Therefore, combinations of both systems are often used as scanner units in ophthalmic devices.

[0023] The most commonly used deflection systems in ophthalmic scanners, as described in US 2008 / 231808 A1, are modern galvanometer scanners that employ an optical position detection system. This system, via an electronic control unit, allows for active control of the mirror movement, including the damping of disturbances (US 5,999,302 A). A further disadvantage of these systems is their complexity and high cost.

[0024] However, the use of simple scanner systems, which can deflect the sample beams simultaneously in two directions, has the disadvantage that the increased number of bearings and the size of the suspensions make it extremely difficult to achieve a sufficiently rigid design with tolerances that are much smaller than the wavelength and thus in the submicrometer range, so that minimizing axial modulations is hardly possible.

[0025] Such a simple scanner system is described, for example, in the unpublished document DE 10 2009 041 995 A1. The optical deflection unit is intended particularly for ophthalmological diagnostic and therapeutic devices and comprises a deflection mirror, a position sensor, and a control unit, which together form a control loop to minimize the deviation of the actual positions detected by the position sensor from the desired positions of the deflection mirror. The optical deflection unit consists of a deflection mirror that can be moved by contactless, electromagnetic drives about at least one axis of rotation and is arranged between at least two bearings in the direction of this axis of rotation.

[0026] US patent 2009 / 225324 A1 describes a high-speed endoscope for optical coherence tomography (OCT) based on a dual-axis micromirror. Since the dual-axis micromirror is typically moved at frequencies between 100 and 1000 Hz, a fast OCT method is required for data acquisition. A multifunctional SD-OCT system is used for this purpose, enabling the creation of three-dimensional, intensity- and polarization-sensitive tomograms.

[0027] It is known from the prior art that significant signal losses due to so-called "fringe washout" are to be expected in OCT when optical path length modulations of more than wavelength fractions per acquired A-scan are used. SH Yun et al. document in [3] that the effect can be so severe that complete signal loss is possible with optical path length variations of λ / 2 per acquired A-scan, as constructive and destructive interferences may average out. Literature: [1] AH Bachmann, ML Villiger, C. Blatter, T. Lasser and RA Leitgeb, “Resonant Doppler flow imaging and optical vivisection of retinal blood vessels”, Vol. 15, No. 2 / OPTICS EXPRESS 408. [2] SH Yun, GJ Teamey, JF de Boer, and BE Bouma, “Pulsedsource and swept-source spectral-domain optical coherence tomography with reduced motion artifacts,” Vol. 12, No 23 / OPTICS EXPRESS 5614. [3] SH Yun, GJ Tearney, JF de Boer, and BE Bouma, “Motion artifacts in optical coherence tomography with frequency-domain ranging,” Vol. 12, No. 13 / OPTICS EXPRESS 2980. [4] Lin An and Ruikang K. Wang, “Use of a scanner to modulate spatial interferograms for in vivo full-range Fourier-domain optical coherence tomography,” Vol. 32, No. 23 / OPTICS LETTERS

[0028] The present invention is based on the objective of developing an OCT-based ophthalmological measurement system in which the influence of occurring axial modulations of the scan system is compensated or at least minimized.

[0029] This task is solved with the OCT-based ophthalmological measurement system, consisting of a light source with a center-of-mass wavelength λ, an interferometric measurement arrangement, a scanner system which, in addition to the lateral deflection of the sample beam, also causes axial modulations with a frequency f in the sample arm, and a control and evaluation unit, by the fact that the measurement system is a swept-source OCT system and the tuning time dλ / dt of the tunable light source is adapted to the desired maximum measurement depth z and the frequency f of the axial modulation of the scanner system.

[0030] According to the invention, the problem is solved by the features of the independent claims. Preferred embodiments and configurations are the subject of the dependent claims.

[0031] A particularly advantageous configuration results when the amplitude z MThe axial modulation of the scanner system is smaller than the resolution δz of the swept-source OCT system. The tuning times dλ / dt of the light source can be significantly different even with axial modulation at frequencies f between 100 Hz and 10,000 Hz, provided that λ is at least 100 Hz. 2 * f / (4z) and especially also via λ 2 * f / z. To adapt the tuning times of the light source to expected modulation frequencies, the latter can also be determined by analyzing mechanical resonances using computer simulation, for example using FEM (Finite Element Method).

[0032] The application of the proposed OCT-based measurement system is intended particularly for the field of ophthalmology, specifically for determining distances or for tomographic imaging of eye structures.

[0033] Particularly in this area, the solution offers the possibility of using cost-effective scanner systems, which significantly simplifies the overall device setup.

[0034] However, the proposed measurement system is also applicable to scanner systems in other fields that can use an OCT method, in particular a swept-source OCT method.

[0035] The invention is described in more detail below with reference to exemplary embodiments. To better illustrate the inventive solution, the figures show B-scans of a glass plate: Fig. 1: when using a scanner system with an amplitude z M the axial modulation of z M > λ / 10, especially z M = ± 2µm, Fig. 2: when using a scanner system with an amplitude z M the axial modulation of z M >> λ / 2, especially z M = ± 10µm and Fig. 3: when using a state-of-the-art ophthalmic measuring system with an amplitude z M the axial modulation of z M > λ / 2, especially z M = ± 10µm.

[0036] The OCT-based ophthalmological measurement system according to the invention consists of a light source with a center-of-mass wavelength λ, an interferometric measurement arrangement, a scanner system which, in addition to lateral deflection of the sample beam, also features axial modulations with a frequency f in the sample arm, and a control and evaluation unit. The scanner system in this context refers to systems that achieve lateral, two-dimensional deflection of the sample beam using one or two separate mirror elements and, in particular, axial modulation amplitudes z. M >> can exhibit λ / 2.

[0037] A swept-source OCT system is used as the measurement system. The tuning time dλ / dt of the tunable light source is adapted to the desired maximum measurement depth z and the frequency f of the axial modulation of the scanner system.

[0038] In ophthalmology, the desired maximum measuring depth z depends on the length of the eye being measured, which typically varies between approximately 20 and 32 mm (with extreme variations between 14 and 40 mm), taking into account the refractive indices of the ocular media. Assuming a mean refractive index of 1.36 and an adjustment range of 5 mm in air, the required optical measuring depth z is approximately 60 mm.

[0039] This keeps the "dwell time" of the measurement system at each modulation of the interference signal small compared to the mechanical modulation frequencies f of the scanner system. The effects of "fringe washout" can thus be avoided, even though the total acquisition time for an A-scan can be significantly greater than 1 / f.

[0040] For ophthalmology, it is advantageous that the center wavelength λ of the light source lies in a range of 700 nm to 900 nm, particularly at 800 nm, or in a range of 1000 nm to 1100 nm, particularly at 1060 nm. The light source preferably has a bandwidth Δλ of 3 nm to 100 nm around the center wavelength λ.

[0041] By using a swept-source OCT system as an ophthalmological measurement system, and by adjusting the tuning time dλ / dt of the light source to the measurement depth z and the frequency f of the axial modulation of the scanner system, scanner systems can be used whose axial modulation amplitude z M can be significantly more than just fractions of the wavelength λ. In particular, the amplitude z M the axial modulation of the scanner system during the tuning time dλ / dt may be more than λ / 10 to λ / 2, even more than 1µm.

[0042] In a particularly advantageous embodiment of the ophthalmological measuring system according to the invention, the amplitude z M the axial modulation of the scanner system is smaller than the resolution δz of the swept-source OCT system, which can be determined according to the following equation: δz=2*ln(2)*λ2 / (Δλ*π) where Δλ corresponds to the bandwidth of the light source. The axial modulations do not lead to a reduction in the axial resolution δz of the swept-source OCT system.

[0043] In principle, measurements are also possible with the solution according to the invention if the amplitude z M The axial modulation of the scanner system is greater than the resolution δz of the swept-source OCT system. The tuning time dλ / dt of the light source, adapted to the desired maximum measurement depth z and the frequency f of an axial modulation of the scanner system, is at least dλ / dt = λ, even for axial modulation frequencies f between 100 Hz and 10,000 Hz. 2 * f / 4z and especially also via dλ / dt = λ 2 * f / z. This condition can also be met for multiple frequencies if several axial modulations are superimposed.

[0044] This is shown by the Fig. One to three B-scans of a glass plate. Since the thickness of the glass plate and the maximum measurement depth of z=10mm are greater than the area shown, only sections of the B-scans with an interface are displayed.

[0045] These were obtained using a swept-source OCT system (SS-OCT), a tunable light source with a center-of-mass wavelength λ=1µm and a tuning time dλ / dt=30nm / ms, and a scanner system with a modulation amplitude z M recorded from more than λ / 10.

[0046] With a resolution of the swept-source OCT system of δz=7µm / pixel, the lateral scan speed was 10µm / pixel or 1 ms / pixel.

[0047] The in Fig. The B-scans shown in Figure 1 were obtained using a scanner system with a modulation frequency f of 200 Hz to 2000 Hz and a modulation amplitude of z. M = ± 2µm recorded. The signal intensity is uniform from Fig. 1 shows that neither the amplitude z M The frequency f of the axial modulation of the scanner system in the ophthalmological measurement system according to the invention could not have an influence on signal acquisition. A reduction in the axial resolution of the SS-OCT system as a result of the axial modulations of the scanner system was also not observed.

[0048] In contrast, the Fig. 2 B-scans, which were also recorded using a scanner system with a modulation frequency f of 200Hz to 2000Hz, however its modulation amplitude z is M = ± 10µm.

[0049] How the signal pattern of Fig. As can be seen in section 2, measurements are also possible in principle if the modulation amplitude z MThe scanner system's resolution is greater than the resolution δz of the swept-source OCT system. This does result in shifted interface signals in the B-scan and thus an irregular signal waveform. However, a so-called "fringe washout" or even a complete signal loss, as seen in the prior art, does not occur.

[0050] Although at larger modulation amplitudes z M Since the scanner system, especially when its dimensions are larger than the resolution δz of the swept-source OCT system, is likely to be affected by displacement, the inventive solution can still ensure that a continuous signal profile with respect to intensity can be recorded.

[0051] In a particularly advantageous embodiment, the OCT-based ophthalmological measurement system features an additional, known reference structure. The interferometric measurement setup is designed to simultaneously generate reference structure signals from the additional, known reference structure and measurement signals from the eye. The control and evaluation unit is capable of evaluating the disturbances in the reference structure signals caused by the axial modulations of the scanner system and using them to correct the measurement signals from the eye. The reference structure has at least one interface and is preferably a flat glass plate.

[0052] The reference structure signals generated at the (planar) interface directly reflect the disturbances caused by the axial modulations of the scanner system. The correction of the measurement signals generated by the eye can therefore be achieved through simple (identical) shifts. Interpolation can even be used to achieve shifts of fractional pixels.

[0053] In a first embodiment of this approach, the reference structure is positioned in front of the eye. During the measurement process, the reference structure is simply "measured along with the eye" because the interface of the flat glass plate serving as the reference structure reflects a portion of the measurement beam back as a reference structure signal. The generation of the reference structure signals occurs before and / or after the eye, i.e., on the path of the measurement light and / or the path of the light returning to the eye.

[0054] In a second embodiment, the OCT-based ophthalmological measurement system features an element for extracting a portion of the measurement beam, enabling the interferometric measurement setup to simultaneously generate reference structure signals from an additional, known reference structure and measurement signals from the eye. The control and evaluation unit is capable of analyzing the disturbances in the reference structure signals caused by the axial modulations of the scanner system and using them to correct the measurement signals from the eye.

[0055] Preferably, the element for extracting a portion of the measuring beam is arranged downstream of the scanner system. A suitable design and / or illumination of the reference structure ensures that reproducible reference structure signals can be obtained.

[0056] This makes it possible to further reduce the influence of the scanner system's axial modulations on the measurement results. To achieve this, a portion of the measurement beam is used to simultaneously measure a reference structure of known shape alongside the sample. The control and evaluation unit then uses the acquired reference structure signals to determine shape deviations of the reference structure and to correct the measurement signals from the eye.

[0057] The in Fig. Figure 3, a schematic diagram, serves to better illustrate the advantages of the inventive solution by showing a possible signal waveform when recording B-scans of a glass plate according to the Fig. 1 and Fig. 2, however, using a measurement system known from the state of the art, such as a non-pulsed SD-OCT, shows.

[0058] As already explained and the Fig.As can be seen in section 3, optical path length modulations of the scanner system of more than fractions of a wavelength can lead to so-called "fringe washout" or even to complete signal loss (dark signal dropout areas) in OCT.

[0059] In a particularly advantageous embodiment, a simple scanner system with only one deflection mirror is used for the proposed OCT-based measuring system. Such a simple scanner system is described, for example, in the unpublished document DE 10 2009 041 995 A1. The optical deflection unit here is a deflection mirror that can be pivoted about at least one, but preferably two, axes of rotation.

[0060] The ophthalmological measuring system according to the invention provides a solution with which the influence of occurring axial modulations of the scanning system is compensated or at least minimized when determining distances or for tomographic imaging of eye structures based on an OCT method.

[0061] This was achieved by using a swept-source OCT system as a measurement system in conjunction with a tunable light source, whereby the tuning time dλ / dt of the light source is adapted to both the maximum measurement depth z and the modulation frequency f of the scanner system.

[0062] No solutions are currently known in the art where scanner systems with large axial modulations, which can be in the micrometer range, are successfully used.

[0063] The proposed technical solution is particularly interesting for scanner systems that deflect the sample beams simultaneously in two directions. With these systems, which consist of only a single mirror element, the increased number of bearings and the size of the suspension make a sufficiently rigid design for axial modulations, especially those exceeding wavelength fractions or in the sub-micrometer range, extremely difficult.

[0064] The proposed solution will make it possible to implement scanners, especially for OCT systems, at a significantly lower cost if, in addition to the required angular deflection, axial path length modulations of significantly more than just fractions of the wavelength are also permitted.

Claims

[1] OCT-based ophthalmological measurement system, comprising a light source with a center-of-mass wavelength λ, an interferometric measurement arrangement, a scanner system which, in addition to the lateral deflection of the sample beam, also causes axial modulations with a frequency f in the sample arm, and a control and evaluation unit, characterized in that the measurement system is a swept-source OCT system and the tuning time dλ / dt of the tunable light source is adapted to the desired maximum measurement depth z and the frequency f of the axial modulation of the scanner system, and the amplitude z M the axial modulation of the scanner system during the tuning time dλ / dt is more than λ / 10 to λ / 2 and in particular also more than 1µm. [2] OCT-based ophthalmological measurement system according to claim 1, characterized in that the center wavelength λ of the light source is in a range of 700nm to 900nm, in particular at 800nm ​​or in a range of 1000nm to 1100nm, in particular at 1060nm. [3] OCT-based ophthalmological measurement system according to one of claims 1 and 2, characterized in that the light source has a bandwidth Δλ of 3nm to 100nm around the center wavelength λ. [4] OCT-based ophthalmological measurement system according to one of the preceding claims, characterized in that the amplitude z M the axial modulation of the scanner system is smaller than the resolution δz of the swept-source OCT system, δz=2*ln(2)*λ2 / (Δλ*π) where Δλ corresponds to the bandwidth of the light source. [5] OCT-based ophthalmological measurement system according to one of the preceding claims, characterized in that the tuning time dλ / dt of the light source with expected axial modulation with frequencies f between 100Hz and 10,000Hz, is at least λ 2 *f / (4z) and especially also via λ 2 * f / z is. [6] OCT-based ophthalmological measurement system according to one of the preceding claims, characterized in that an additional, known reference structure is provided and the interferometric measurement arrangement is designed such that reference structure signals of the additional, known reference structure and measurement signals from the eye can be generated simultaneously and the control and evaluation unit is able to evaluate the disturbances of the reference structure signals caused by the axial modulations of the scanner system and to use them to correct the measurement signals from the eye. [7] OCT-based ophthalmological measurement system according to claim 6, characterized in that the reference structure has at least one interface. [8] OCT-based ophthalmological measurement system according to claim 6, characterized in that the reference structure is a flat glass plate. [9] OCT-based ophthalmological measurement system according to one of claims 6 to 8, characterized in that the reference structure is arranged in front of the eye. [10] OCT-based ophthalmological measurement system according to one of the preceding claims, characterized in that an element for coupling out a part of the measurement beam is provided, so that reference structure signals of the additional, known reference structure and measurement signals from the eye can be generated simultaneously by the interferometric measurement arrangement and the control and evaluation unit is able to evaluate the disturbances of the reference structure signals caused by the axial modulations of the scanner system and to use them to correct the measurement signals from the eye. [11] OCT-based ophthalmological measuring system according to claim 10, characterized in that the element for coupling out a part of the measuring beam is arranged after the scanner system.

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